GATE CH topic:mass-transfer PYQs & Answers — Page 6

Questions 51–60 of 77. Imported answers require independent review unless marked reviewed.

SO₂ from air is absorbed by pure water in a counter current packed column operating at constant pressure. The compositions and the flow rates of the streams are shown in the figure.

Diagram for Chemical Engineering question 28

In addition, use the following data and assumptions • Column operates under isothermal conditions • At the operating temperature of the column,

, where

is the mole fraction of SO₂ in the gas that is in equilibrium with water containing SO₂ at a mole fraction of

• Solution is dilute and the operating line is linear • Negligible amount of water evaporates

The number of transfer units (NTU) for this column is

Your answerChoose one option.

0.5

1.0

1.5

2.0

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Two film theory applies for absorption of a solute from a gas mixture into a liquid solvent. The interfacial mass transfer coefficient (in mol m⁻² s⁻¹) for the gas side is 0.1 and for the liquid side is 3. The equilibrium relationship is

, where

and

are mole fractions of the solute in the liquid and gas phases, respectively. The ratio of the mass transfer resistance in the liquid film to the overall resistance is

Your answerChoose one option.

0.0161

0.032

0.0625

0.0645

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Consider the equilibrium data for methanol-water system at 1 bar given in the figure below.

Diagram for Chemical Engineering question 30

A distillation column operating at 1.0 bar is required to produce 92 mol % methanol. The feed is a saturated liquid. It is an equimolar mixture of methanol and water. The minimum reflux ratio is

Your answerChoose one option.

0.33

0.50

0.54

1.17

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Equilibrium data for a binary mixture of E and F at two different pressures is shown in the figure.

It is desired to process a feed containing 80 mol % E and 20 mol % F, and obtain a product with a purity of 99.5 mol % E. A sequence of two distillation columns, one operating at pressure

and another at

, is employed for this operation, as shown below.

The mole fraction of E in the distillate obtained from column 1 is 0.9. If the column pressures

and

are in kPa, which one of the following is correct?

Diagram for Chemical Engineering question 34

Your answerChoose one option.

, and high purity E is recovered from the top of column 2

, and high purity E is recovered from the bottom of column 2

, and high purity E is recovered from the top of column 2

, and high purity E is recovered from the bottom of column 2

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Two ideal cross-current stages operate to extract P from a feed containing P and Q, as shown below.

Diagram for Chemical Engineering question 47

The mass flow rates of P and Q fed to Stage 1 are 1,000 kg h

and 10,000 kg h

, respectively. Pure solvent (S) is injected at mass flow rates of 5,000 kg h

and 15,000 kg h

to Stages 1 and 2, respectively. The components Q and S are immiscible. The equilibrium relation is given by

, where

is the mass of P per unit mass of Q in the raffinate, and

is the mass of P per unit mass of S in the extract, which is in equilibrium with the raffinate. The mass flow rate of P (in kg h

) in the raffinate from Stage 2 is ________ (round off to nearest integer).

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Consider a vertically falling film of water over an impermeable wall. The film is in contact with a static pool of non-reactive pure gas. The gas diffuses into the water film over the entire height of the falling film. The height of the film is 1.0 m, and its thickness is

m. The velocity of water, averaged over the film thickness, is 0.01 m s

. The gas concentration (in kg m

), averaged over the film thickness is

where

is the vertical position in meters measured from the top of the wall.

In addition, use the following data and assumptions:

The flow is fully developed

The width of the film is much larger than the thickness of the film, and the dissolved gas concentration is invariant over this width

The solubility of the gas in water,

, is constant

Pure water enters at

The evaporation of water is negligible

The mass transfer coefficient on the liquid side (in mm s

), averaged over the entire height of the falling film is ________ (round off to 3 decimal places).

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The correct expression for the Colburn

-factor for mass transfer that relates Sherwood number (Sh), Reynolds number (Re) and Schmidt number (Sc) is

Your answerChoose one option.

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In the drying of non-dissolving solids at constant drying conditions, the internal movement of moisture in the solid has a dominant effect on the drying rate during

Your answerChoose one option.

the initial adjustment period only

the constant rate period only

the falling rate period only

both the initial adjustment and constant rate periods

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Three distillation schemes for separating an equimolar, constant relative volatility ABC mixture into nearly pure components are shown. The usual simplifying assumptions such as constant molal overflow, negligible heat loss, ideal trays are valid. All the schemes are designed for minimum total reboiler duty. Given that the relative volatilities are in the ratio

, the correct option that arranges the optimally-designed schemes in ascending order of total reboiler duty is

Diagram for Chemical Engineering question 15

Your answerChoose one option.

I, II, III

III, I, II

II, I, III

III, II, I

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100 kg of a feed containing 50 wt.% of a solute C is contacted with 80 kg of a solvent containing 0.5 wt.% of C in a mixer-settler unit. From this operation, the resultant extract and raffinate phases contain 40 wt.% and 20 wt.% of C, respectively. If E and R denote the mass of the extract and raffinate phases, respectively, the ratio E/R is

Your answerChoose one option.

1/4

1/2

2/3

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GATE CH topic:mass-transfer PYQs

Question 28

Question 29

Question 30

Question 34

Question 47

Question 48

Question 13

Question 14

Question 15

Question 32